The present invention relates to ceramic based multi-site electrode arrays comprising a polished ceramic substrate which is patterned with metal recording sites, conducting lines and bonding pads. The electrode arrays of the present invention are useful in recording large numbers of neurons simultaneously in mammalian central nervous system tissue. Further the electrode arrays of the present invention are useful for chronic stimulation of small regions of neural tissue using small currents. Methods for producing the multi-site ceramic based electrode arrays via reverse photolithography are also provided.
Although many different types of electrodes have been designed for recording and stimulating mammalian central nervous system tissue (see e.g. Moxon, K.A. Multiple-site recording electrodes in Methods for simultaneous neuronal ensemble recordings Eds. M.A.L. Nicolelis, CRC Press, Boca Raton, Fla. 1999), traditional chronic recording electrodes consist of a gold, platinum or stainless steel wire coated with an insulating material, usually Teflon, except at the tip. While these electrodes function adequately in many situations, they suffer drawbacks that reduce their usefulness as neural interface devices. These drawbacks include a low recording site (RS) to neuronal tissue displaced (NTD) ratio, difficulty of integrating on board electronics sufficiently close to the electrode to reduce noise, and the inability to produce quality microwire electrodes for neural recording using batch processing. Generally these electrodes are made by hand, resulting in considerable variation in the recording characteristics of each electrode tip. Further, since on board electronics will ideally be included, a wide range of electrical characteristics of the electrode results in difficulties properly matching impedances.
Thin-film electrodes have also been developed to record neuron activity (Pickard, R. S. and Welberry, T. R. J. Exp. Biol. 1976 64:39; Pickard, R. S. J. Neurosci. Meth. 1979 1:301; Llinas et al. Implantable monolithic wafer recording electrodes for neurophysiology in Brain unit activity during behavior, Eds. M. I. Philips and C. C. Thomas, I11, 1973; Najafi et al. IEEE Trans. Electron Dev. 1985 32:1206; Wise, K. D. and Angell, J. B. IEEE Trans. Biomed. Eng. 1970 BME-17(3):238; Campbell et al. Proc. 27th Annu. Rocky Mountain Bioeng. Symp. and the 27th Int. ISA Biomed. Sci. Inst. Symp. Denver, Colo., Apr. 6-7, 1990, 161; BeMent et al. IEEE Trans. Biomed. Eng. 1986 33(2):230; and Campbell et al. IEEE Trans. Biomed. Eng. 1991 38(8):758) However, the majority of these electrodes are built on silicon substrates and have not been shown to be useful for chronic stimulation and recording of single neurons.
In the present invention, a multi-site electrode array is provided which comprises a polished ceramic substrate patterned with recording sites, conducting lines and bonding pads. This thin film electrode has the ability to maintain the brain-electrode interface at a high RS/NTD ratio, records chronically from single neurons for up to 3 months, and uses a substrate material and insulation that is strong and resistant to the brain microenvironment. The electrode of the present invention is the same size as a single microwire but has multiple recording sites and can be integrated with onboard electronics in a very large scale integration (VLSI) circuit.
An object of the present invention is to provide a ceramic based multi-site electrode array useful in recording and/or stimulating large numbers of neurons simultaneously.
Another object of the present invention is to provide a method for producing ceramic based multi-site recording electrode arrays comprising patterning a polished ceramic substrate with recording sites, conducting lines and bonding pads via image reverse photolithography following by application of a metal layer and an insulating layer.